The present invention concerns a device and method for communicating at a distance and systems using them. It is situated mainly in the field of wireless networks.
In an office environment the characteristics of propagation and attenuation of electromagnetic waves are continually changing. For radio communications indoors, the electromagnetic waves can take a multitude of possible paths (particularly at certain frequencies). The different waves which arrive at the antenna of the receiver interfere constructively or destructively. Consequently, at some points, the signal is greatly attenuated, which is what is referred to as fading.
If the antenna of the receiver is situated in a fade area, the signal received is too greatly attenuated for the radio communication to be able to take place.
There are many means for mitigating the problems of multiple paths. Notably antenna diversity, frequency jumping etc.
The document U.S. Pat. No. 5,437,055 describes a system for minimising the effects of multiple paths. For this purpose the author proposes to provide the antenna with a real or simulated movement. In order to simulate the movement, the inventor proposes to vary the phase of the signal, which makes it possible to change the apparent position of the antenna, without moving physically.
In such networks, the signals are reflected by the walls and absorbed by certain materials, and problems of signal fading arise (these problems are related to the interference signals which have followed different parts).
During a given interval of time, at a few centimeters distance, the reception of the same signal sent can thus be of good quality or poor quality.
The present invention aims to remedy these drawbacks.
To this end, the present invention relates, according to a first aspect, to a device for communicating at a distance having a signal transmission/reception means, characterised in that the said transmission/reception means has a moving part and a receiving device, the said moving part cyclically modifying the electromagnetic environment of the said receiving device.
The movement given to the antenna prevents it being situated in a fade area throughout the period of transmission of the data. This makes it possible to obtain a mean value of the received signal so as to increase the robustness of the radio transmission.
The document U.S. Pat. No. 5,437,055 proposes, in a preferred embodiment, to fix the antenna to a rotating part. However, it provides no teaching concerning the moving part. In fact, it does not indicate how to choose and control the speed of rotation of the antenna, according to the quality of reception. The invention described here gives the method and means of choosing and controlling the speed.
According to the invention, if the antenna of the receiver is situated in a fade area (the signal received is then too attenuated for radio communication to be able to take place), the antenna of the receiver or transmitter is moved in order to move out of this fade area and to regain correct conditions so as to ensure the transmission of data.
The method and device thus make it possible to get rid of the problems of multiple paths by providing a movement, for example for the reception antenna.
This is because, when the radio data transmission device is associated with an appliance (copier, facsimile machine, printer etc) having at least one moving part, it is possible to use the latter in order to fix the receiver antenna thereto. The movement of the antenna thus makes it possible to use an average of the fading effects.
According to a first embodiment, when the office equipment which incorporates the device according to the present invention is in a standby state (no printing or copying) the moving element will be moved so as to place an antenna in an optimum position.
According to a second embodiment, when the office equipment which incorporates the device according to the present invention is in an operating state, the movable element (for example an inertia flywheel) rotates uniformly and an antenna fixed to this will successively be situated in areas of good reception and fading. A first analysis of the fading will enable the device to modify the transmission conditions.
According to a first aspect, the present invention relates to a device for communicating at a distance having a signal transmission/reception means, characterised in that said transmission/reception means has a moving part and a reception device, said moving part modifying the electromagnetic environment of said reception device.
The present invention has the advantage of being simpler than the systems with several antennae or frequency jumping. In addition, it makes it possible to use a moving part of an appliance in order to give it an additional function.
According to particular characteristics, said moving part is an antenna. By virtue of these provisions, said antenna can move from a minimum to a maximum communication quality.
According to other particular characteristics, said moving part is fixed to a moving component of an item of office equipment, said office equipment using data received by means of said communication device.
Thus the present invention is particularly easy to implement.
According to other particular characteristics, said moving part effects a cyclic movement so that the modification to the electromagnetic environment caused by said movement has the same cycle period as the movement of said moving part.
By virtue of these provisions, the antenna regularly returns to a good communication area.
According to other particular characteristics, the device according to the invention, as succinctly disclosed above, has a means of determining a mean duration of periods of good communication.
By virtue of these provisions, communication parameters can be adjusted according to said duration.
According to other particular characteristics, the communication device as succinctly disclosed above has a frame duration determination means, adapted so that said frame duration is less than or equal to the mean duration of the periods of good communication.
By virtue of these provisions a frame can be communicated during the majority of the periods of good communication.
According to other particular characteristics, the communication device as succinctly disclosed above has:
a means of determining a new cycle duration equal to or greater than the product of the former cycle duration and the ratio of the duration of a data frame, used by the communication means, to the period of good communication, and
a means of controlling the duration of the cycle adapted to compel said cycle to have said new cycle duration.
By virtue of these provisions, a frame can be communicated during the majority of the periods of good communication.
According to other particular characteristics, the communication device as succinctly disclosed above has:
a good communication cycle ratio determination means, adapted to determine the mean ratio of the duration of good communication during a cycle over the duration of said cycle, and
a means of determining a ratio of redundancy information associated with data to be communicated, said ratio being a function of the good communication cycle ratio.
By virtue of these provisions, the number of items of redundancy information necessary for the correction of errors caused by communication quality defects can be associated with the data to be communicated.
According to particular characteristics, the communication device as succinctly disclosed above has a good communication determination means and, when said good communication determination means determines that the communication is not good, said moving part is set in movement.
By virtue of these provisions, when the communication is good, the moving part can remain in place whilst, when the communication is not of good quality, the moving part is set in movement in order to adopt a position where the communication is of good quality.
According to a second aspect, the present invention relates to a method of communicating at a distance characterised in that it includes a step of setting in movement a moving part of a signal transmission/reception means.
The invention also relates to a network, a computer, a copier, a facsimile machine, a printer, a scanner, a camera and an information terminal, characterised in that they have a device as succinctly disclosed above.
The invention also relates to:
an information storage means which can be read by a computer or microprocessor storing instructions of a computer program characterised in that it makes it possible to implement the method of the invention as succinctly disclosed above, and
an information storage means which is removable, partially or totally, and which can be read by a computer or microprocessor storing instructions of a computer program characterised in that it makes it possible to implement the method of the invention as succinctly disclosed above.
The preferential or particular characteristics, and the advantages of this device, this network, this computer, this copier, this facsimile machine, this printer, this scanner, this camera, this information terminal and these information storage means being identical to those of the method as succinctly disclosed above, these advantages are not repeated here.